...with inline children. This fixes an issue when we ignore abspos boxes
contained by PaintableWithLines while calculating overflow rect size.
Lots of layout tests are affected, because now PaintableWithLines has
overflow rect.
`Text/input/DOM/Element-set-scroll-left.html` is also affected and now
matches other browsers.
When a block container has `clear` set and some clearance is applied,
that clearance prevents margins from adjoining and therefore resets
the margin state. But when a floating box has `clear` set, that
clearance only goes between floating boxes so should not reset margin
state. BlockFormattingContexts already do that correctly, and this PR
changes InlineFormattingContext to do the same.
Fixes#1462; adds reduced input from that issue as test.
